Induction of anti-leukemic responses by stimulation of leukemic CD3+ cells with allogeneic stimulator cells

Background

Immunotherapeutic protocols have focused on identification of stimuli that induce effective anti-leukemic immune responses. One potent immune stimulus is the encounter with allogeneic cells. Our group previously showed that the infusion of haploidentical donor white blood cells (1-2 × 10⁸ CD3+ cells/kg) into patients with refractory hematological malignancies induced responses of varying magnitude in over half of the patients. Because donor cells were eliminated within 2 weeks in these patients, it is presumed that the responses of recipient lymphocytes were critically important in achieving prolonged anti-leukemic responses.

Methods

The role of patient CD3+ cells in anti-leukemic responses was examined by isolating peripheral blood mononuclear cells from newly diagnosed leukemic patients. Immunophenotyping was performed on these peripheral blood mononuclear cells. CD3+ cells were isolated from the peripheral blood mononuclear cells and tested for their ability to proliferate and lyse autologous leukemic cells when stimulated with unrelated allogeneic cells.

Results

Allostimulated CD3+ cells effectively generated cytolytic responses to autologous CD3-cells in 11/21 patients. Increased numbers of CD4+ cells expressing high levels of granzyme A, B and perforin and CD8+CD39+ cells were found in nonresponsive CD3+ cells.

Conclusions

These results indicate that CD3+ cells from leukemic patients are capable of generating anti-leukemic responses when stimulated with unrelated allogeneic cells. This model can be used to identify approaches using alloreactive responses by patient lymphocytes to enhance in vivo anti-leukemic responses.

Dissecting the use of recipient alloreactive responses to achieve anti-leukemic effect

Harnessing alloreactive responses to incur anti-leukemic effects has focused on the donor lymphocyte response directed toward recipient antigens. Limited studies have examined the anti-leukemic potential of recipient alloreactive responses to donor cell antigens. An example is the infusion of large numbers of haploidentical, G-CSF mobilized, donor T cells (1 – 2 × 108 CD3+ cells/kg) into patients with refractory hematological malignancies who had received100 cGy total body irradiation prior to infusion. Strong recipient immune responses were generated capable of eliminating the donor cells within two weeks (thereby preventing GVHD) with side effects of high fever (104°F), malaise, rash, and diarrhea. More than half of these patients also generated responses to the hematological malignancies(14/26, 9 major), including some complete remissions. The protocol was modified in the reopened clinical trial by elimination of both the G-CSF mobilization of donor cells and the recipient 100 cGy total body irradiation. These patients exhibited milder, self-resolving fevers and limited anti-leukemic responses (1/5 with transient response). Analysis of blood samples obtained at several different timepoints after infusion revealed diminished IL-6 levels. Increased levels of plasma IL-2 and granzyme B and increased expression of granzyme B and PD-1 by activated recipient T cells correlated with elimination of donor cells. Increased expression of PD-1 ligands on leukemic cells provides one explanation for the lack of anti-leukemic response. These results indicate that appropriate manipulation of both donor cells and patients in this protocol should improve the anti-leukemic responses of recipient lymphocytes.

Abstract A14: Cellular immunotherapy for refractory hematological malignancies: Haploidentical donor lymphocyte infusions generate an allogeneic effect that targets leukemia

Background/Objective: Allogeneic stem cell transplantation (allo-SCT) is an effective treatment modality for leukemia and lymphoma that exerts much of its therapeutic benefit via a graft versus tumor response. Its applicability is limited by toxicity from preconditioning chemoradiation and graft versus host disease. We present data from a Phase II IRB and FDA approved clinical trial in which haploidentical allogeneic cells are infused into patients with refractory hematologic malignancies without prior chemotherapy or radiation. The goal is to generate a robust allogeneic response created via donor cell rejection that breaks host tumor tolerance without the toxicity profile seen in allo-SCT.

Methods: Eligible patients have refractory acute leukemias and aggressive systemic lymphomas without curative options. HLA haploidentical donors are identified then undergo leukapheresis without stem cell mobilization. 1-2x108 CD3+ cells/kg are infused unprocessed immediately following collection. Peripheral blood samples collected 1, 24, 48, 72 and 168 hours after infusion are examined for effector cell populations, stimulatory/inhibitory signals, and cytokine release profiles.

Results: Three patients have been infused haploidentical cells. Two developed hyperpyrexia following treatment that persisted for 48 hours. One of three patients demonstrated a decrease in peripheral blood and bone marrow blast counts following therapy (Reduction in peripheral absolute blast count from 3900/uL to 1200/uL and bone marrow blasts from 43% to 21% four weeks post therapy). No Grade 3 or 4 toxicities or durable chimerism was seen. Host T cells demonstrated cytolytic effector molecule expression but little cytolytic activity, possibly secondary to rapid up-regulation of PD-1 and PD-1 ligands by host CD8+ cells and leukemia cells, respectively.

Discussion: Haploidentical donor cellular infusions are well tolerated and demonstrate biological activity in relapsed leukemia. Lab correlative studies suggest potential future mechanisms to augment response involving PD-1 blockade. Our method provides a true bench to bedside approach utilizing adoptive immunotherapy created via a host allogeneic rejection response.

Citation Format: John L. Reagan, Loren D. Fast, Martha Nevola, Andrew Schumacher, Kayla Rosati, Howard Safran, Matt I. Quesenberry, Eric P. Winer, James N. Butera, Peter J. Quesenberry. Cellular immunotherapy for refractory hematological malignancies: Haploidentical donor lymphocyte infusions generate an allogeneic effect that targets leukemia. [abstract]. In: Proceedings of the AACR Special Conference on Hematologic Malignancies: Translating Discoveries to Novel Therapies; Sep 20-23, 2014; Philadelphia, PA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(17 Suppl):Abstract nr A14.

HCV epitope, homologous to multiple human protein sequences, induces a regulatory T cell response in infected patients

BACKGROUND & AIMS

Spontaneous resolution of hepatitis C virus (HCV) infection depends upon a broad T cell response to multiple viral epitopes. However, most patients fail to clear infections spontaneously and develop chronic disease. The elevated number and function of CD3(+)CD4(+)CD25(+)FoxP3(+) regulatory T cells (T(reg)) in HCV-infected patients suggest a role of Treg cells in impaired viral clearance. The factors contributing to increased Treg cell activity in chronic hepatitis C cases remain to be delineated.

METHODS

Immunoinformatics tools were used to predict promiscuous, highly-conserved HLA-DRB1-restricted immunogenic consensus sequences (ICS), each composed of multiple T cell epitopes. These sequences were synthesized and added to cultures of peripheral blood mononuclear cells (PBMCs), derived from patients who resolved HCV infection spontaneously, patients with persistent infection, and non-infected individuals. The cells were collected and following 5days incubation, quantified and characterized by flow cytometry.

RESULTS

One immunogenic consensus sequence (ICS), HCV_G1_p7_794, induced a marked increase in Treg cells in PBMC cultures derived from infected patients, but not in patients who spontaneously cleared HCV or in non-infected individuals. An analogous human peptide (p7_794), on the other hand, induced a significant increase in Treg cells among PBMCs derived from both HCV-infected and non-infected individuals. JanusMatrix analyses determined that HCV_G1_p7_794 is comprised of Treg cell epitopes that exhibit extensive cross-reactivity with the human proteome.

CONCLUSIONS

A virus-encoded peptide (HCV_G1_p7_794) with extensive human homology activates cross-reactive CD3(+)CD4(+)CD25(+)FoxP3(+) natural Treg cells, which potentially contributes to immunosuppression and to the development of chronic hepatitis C.

Induction of anti-leukemic responses using cellular immunotherapy (TUM2P.921)

Previous work has shown that blood cancers can be treated through stimulation of the cancer patient’s immune system. In initial studies, it was observed that 14/26 patients with refractory hematological malignancies responded (9 major) to the infusion of large numbers (1 -2 x 108 CD3+ cells/kg) of haploidentical white blood cells following low levels of total body irradiation (100cGy). A cytokine storm quickly developed with a median time of 14 hours and resulted in high fevers that were allowed to persist for 48 hours, if possible, and then controlled with corticosteroids if needed. However the potential role of anti-leukemic effector cells in these responses was not determined. Three patients have been enrolled into a re-opened cellular immunotherapy clinical trial in which haploidentical white blood cells are infused with no prior chemotherapy or radiation. Blood samples were obtained from the recipient approximately 1, 24, 48, 72 and 168 hours after infusion and analyzed for the persistence and activity of donor/recipient cells as well as levels of cytokines and other factors in the plasma. Thus far, the results demonstrate elimination of donor cells by day 7, rapid upregulation of PD-1 ligands on leukemic cells and prolonged plasma levels of IL-10. Evaluation of the trends obtained with increased number of patients enrolled in the clinical trials will provide insights into new approaches to enhance the anti-leukemic responses in these patients.

Cellular immunotherapy for refractory hematological malignancies

Background

Acute myeloid leukemia (AML) and other aggressive refractory hematological malignancies unresponsive to upfront therapy remain difficult conditions to treat. Often, the focus of therapy is centered on achieving complete remission of disease in order to proceed with a consolidative stem cell transplant. At issue with this paradigm is the multitude of patients who are unable to achieve complete remission with standard chemotherapeutic options. A major benefit of transplantation is the graft versus tumor effect that follows successful engraftment. However, with this graft versus tumor effect comes the risk of graft versus host disease. Therefore, alternative treatment options that utilize immunotherapy while minimizing toxicity are warranted. Herein, we propose a novel treatment protocol in which haploidentical peripheral blood stem cells are infused into patients with refractory hematological malignancies. The end goal of cellular therapy is not engraftment but instead is the purposeful rejection of donor cells so as to elicit a potent immune reaction that appears to break host tumor tolerance.

Methods/design

The trial is a FDA and institutional Rhode Island Hospital/The Miriam Hospital IRB approved Phase I/II study to determine the efficacy and safety of haploidentical peripheral blood cell infusions into patients with refractory hematological malignancies. The primary objective is the overall response rate while secondary objectives will assess the degree and duration of response as well as safety considerations. Patients with refractory acute leukemias and aggressive lymphomas over the age of 18 are eligible. Donors will be selected amongst family members. Full HLA typing of patients and donors will occur as will chimerism assessments. 1-2x10⁸ CD3+ cells/kilogram will be infused on Day 0 without preconditioning. Patients will be monitored for their response to therapy, in particular for the development of a cytokine release syndrome (CRS) that has been previously described. Blood samples will be taken at the onset, during, and following the cessation of CRS so as to study effector cells, cytokine/chemokine release patterns, and extracellular vesicle populations. Initially, six patients will be enrolled on study to determine safety. Provided the treatment is deemed safe, a total of 25 patients will be enrolled to determine efficacy.

Discussion

Cellular Immunotherapy for Refractory Hematological Malignancies provides a novel treatment for patients with relapsed/refractory acute leukemia or aggressive lymphoma. We believe this therapy offers the immunological benefit of bone marrow transplantation without the deleterious effects of myeloablative conditioning regimens and minus the risk of GVHD. Laboratory correlative studies will be performed in conjunction with the clinical trial to determine the underlying mechanism of action. This provides a true bench to bedside approach that should serve to further enrich knowledge of host tumor tolerance and mechanisms by which this may be overcome.

Trial registration

NCT01685606.

Anti-tumor responses driven by alloreactivity (P2058)

Previous work by our group found that infusion of G-CSF mobilized haploidentical donor white blood cells at a dose of 1 - 2 x 108 CD3+ cells/kg into refractory cancer patients who had received 100 cGy total body irradiation resulted in responses in a majority (14/27, 9 major) of patients with hematological malignancies despite elimination of the donor cells. The effector mechanism(s) responsible for these anti-cancer responses were not determined although it was noted that there was a cytokine storm that appeared within a day following the infusion of cells. One possible mechanism is that the alloreactive response overrides inhibitory mechanisms already in place in the cancer bearing patient allowing cancer reactive effector cells that are already present to become activated and lyse cancer cells. To test if this is the case, T cells were isolated from peripheral blood mononuclear cells obtained from newly diagnosed leukemic patients, mixed with fully allogeneic stimulator cells (from 1 or 2 different donors) and then tested for their ability to proliferate in response to the allogeneic stimulator cells on day five and for their ability to lyse autologous leukemia cells after stimulation for seven days. Anti-leukemic effector cells could be generated in eight out of the sixteen patients enrolled to date. The characteristics of the effector cells and the explanations for the lack of responses in some patients are the subject of current ongoing studies.

Abstract 1252: Random unrelated donor peripheral blood mononuclear cells (PBMC) stimulate cytolytic host T cell activity against leukemia

Introduction: In the treatment of acute leukemia, much of the therapeutic effect of allogeneic stem cell transplantation is centered on engraftment of donor cells into the host, with a resultant graft versus leukemia effect. Work previously done by our group and others has shown the infusion of haploidentical stem cells in patients with acute leukemia results in a cytokine storm and exhibits an anti-tumor effect in the absence of engraftment. Whether the underlying clinical response was due to this cytokine storm or secondary to host or donor effector cell interactions was not determined. We present in vitro data collected from leukemia patients in which patient CD3+ cells are stimulated with randomly selected unrelated normal donor peripheral blood mononuclear cells (PBMC). The stimulated patient CD3+ cells are then collected and tested for their ability to lyse leukemia cells from the patient.

Methods: New leukemia patients were identified through standard pathologic diagnostic criteria. Patient samples were collected and separated into CD3+ and CD3- fractions. Patient CD3+ cells were then placed in a mixed lymphocyte culture and stimulated with mitomycin C treated unrelated normal donor PBMC. Cell proliferation was measured on Day 5. On Day 7, the stimulated patient CD3+ cells were collected and then cultured with Chromium 51 labeled CD3- cells, the bulk of which were leukemic blast cells. Cytolytic activity was measured through Cr51 release assays. Cell lysis was recorded as lytic units/million cells (LU/106), which is inversely related to the effector to target ratio at which 30% cell lysis occurs. Patient demographic data including sex and age in addition to leukemia type, cytogenetics, and molecular markers were recorded.

Results: 10 total patients were enrolled in the study; 8 AML, 1 CML, and 1 CMML. 9 patients underwent ex vivo CD3+ stimulation with 2 separate donor PBMC samples while 1 sample underwent only 1 donor stimulation for 19 total assays. The average white blood cell count was 57,640 cells/uL (range 7,100-336,500 cells/ul) with 4-80% peripheral blasts. 7 out of 19 (37%) assays showed leukemia cell cytolytic activity greater than 1 lytic unit. All 7 successful assays were derived from patients with AML (Table 1).

Conclusions: Patient CD3+ cells stimulated with random unrelated donor PBMC are able to generate a cytolytic anti-leukemia response in a donor dependant fashion. This cytolytic activity appears to be unrelated to host lymphocyte proliferation upon donor antigenic stimulation. Interestingly, of the seven assays with cytolytic activity greater than one lytic unit, four were performed in the two patients with known FLT3 ITD positive leukemia, which has a notoriously poor prognosis. Further studies to elucidate a mechanism of action for cellular therapy are warranted.

Citation Format: John L. Reagan, Loren D. Fast, Martha Nevola, Peter J. Quesenberry. Random unrelated donor peripheral blood mononuclear cells (PBMC) stimulate cytolytic host T cell activity against leukemia. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1252. doi:10.1158/1538-7445.AM2013-1252

Abstract B22: Antitumor responses driven by alloreactivity

Previous work done by our group had found that infusion of G-CSF mobilized haploidentical donor white blood cells at a dose of 1 – 2 x 108 CD3+ cells/kg into refractory cancer patients after 100 cGy total body irradiation resulted in a number of complete and partial responses in those patients with hematological malignancies. These responses occurred despite elimination of the donor cells by 2 weeks after infusion. The effector mechanism(s) responsible for these anti-cancer responses were not determined although it was noted that there was a cytokine storm appearing within a day following infusion of the cells. Alloreactive responses could be driving the anti-cancer responses using a variety of mechanisms. One possible mechanism is that the alloreactive response overrides inhibitory mechanisms present in the cancer patient allowing the existing cancer reactive effector cells to become activated and lyse cancer cells. Alternatively the alloreactive cytolytic T cells could be cross-reacting with the antigens expressed on the tumor cells. To test these possibilities, peripheral blood mononuclear cells (PBMNC) or the CD3+ T cells isolated from the PBMNC of newly diagnosed leukemic patients were mixed with mitomycin C treated fully allogeneic stimulator PBMNC (from 1 or 2 different normal controls chosen at random) or the CD3- cells from the leukemic patients. Their ability to proliferate in response to the allogeneic stimulation was tested on day five and their ability to lyse autologous leukemia cells after stimulation was tested on day seven.

Ten total patients (8 AML, 1 CML, and 1 CMML) were enrolled in the study. The average white blood cell count was 57,640 cells/uL (range 7,100 – 336,500 cells/uL) with 4 -80% peripheral blasts. The results indicated that in 16/20 combinations, leukemic T cells were able to proliferate in response to allogeneic stimulators, however anti-cancer cytolytic activity was only detected in 9/19 evaluable combinations. These results demonstrated that alloreactive responses are able to induce anti-leukemic cytolytic responses by T cells from a subset of leukemic patients. One explanation for the inability of some combinations to generate anti-leukemic cytolytic activity could be the presence of inhibitory mechanisms which could not be overcome by the alloreactive responses. Immunophenotypic analysis of the leukemic T cells did reveal an increased number of T regulatory cells and increases in the expression of inhibitory receptors on the lymphocytes from some of the patients. Alternatively, it may be that the leukemic T cells had not been stimulated with the appropriate allogeneic antigens. An allogeneic stimulator pool comprised of cells from ten different normal donors was prepared and will be used to test whether increasing the number of allogeneic disparities in culture would enhance the ability of the leukemic T cells to generate anti-leukemic responses.

These studies have suggested that cancer-reactive cells can be generated from leukemic patient T cells using alloreactive responses. To further test the role of these effector cells and identify additional effector cells, blood samples will be obtained from patients enrolled in the clinical protocol which is in the process of being restarted, having received FDA approval. Clearer definition and characterization of the anti-cancer effector cells should permit alterations to the protocol that would lead to enhanced anti-cancer responses in an increased number of refractory cancer patients.

Citation Format: Loren D. Fast, John Reagan, Martha Nevola, Peter Quesenberry. Antitumor responses driven by alloreactivity. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr B22.

Treatment of whole blood with riboflavin plus ultraviolet light, an alternative to gamma irradiation in the prevention of transfusion-associated graft-versus-host disease?

BACKGROUND

Exposure of blood products to gamma irradiation is currently the standard of care in the prevention of transfusion-associated graft-versus-host disease (TA-GVHD). Regulatory, technical, and clinical challenges associated with the use of gamma irradiators are driving efforts to develop alternatives. Pathogen reduction methods were initially developed to reduce the risk of microbial transmission by blood components. Through modifications of nucleic acids, these technologies interfere with the replication of both pathogens and white blood cells (WBCs). To date, systems for pathogen and WBC inactivation of products containing red blood cells are less well established than those for platelets and plasma.

STUDY DESIGN AND METHODS

In this study, the in vitro and in vivo function of WBCs present in whole blood after exposure to riboflavin plus ultraviolet light (Rb-UV) was examined and compared to responses of WBCs obtained from untreated or gamma-irradiated blood by measuring proliferation, cytokine production, activation, and antigen presentation and xenogeneic (X-)GVHD responses in an in vivo mouse model.

RESULTS

In vitro studies demonstrated that treatment of whole blood with Rb-UV was as effective as gamma irradiation in preventing WBC proliferation, but was more effective in preventing antigen presentation, cytokine production, and T-cell activation. Consistent with in vitro findings, treatment with Rb-UV was as effective as gamma irradiation in preventing X-GVHD, a mouse model for TA-GVHD.

CONCLUSION

The ability to effectively inactivate WBCs in fresh whole blood using Rb-UV, prior to separation into components, provides the transfusion medicine community with a potential alternative to gamma irradiation.